It is desirable to increase the dietary intake of beneficial nutrients omega-3 polyunsaturated fatty acids (omega-3 PUFA), and omega-3 long chain polyunsaturated fatty acids (LC PUFA). Other beneficial nutrients are omega-6 long chain polyunsaturated fatty acids. As used herein, reference to a long chain polyunsaturated fatty acid or LC PUFA, refers to a polyunsaturated fatty acid having 18 or more carbons. Omega-3 PUFAs are recognized as important dietary compounds for preventing arteriosclerosis and coronary heart disease, for alleviating inflammatory conditions, cognitive impairment and dementia related diseases and for retarding the growth of tumor cells. One important class of omega-3 PUFAs is omega-3 LC PUFAs. Omega-6 PUFAs serve not only as structural lipids in the human body, but also as precursors for a number of factors in inflammation such as prostaglandins, and leukotrienes.
Fatty acids are carboxylic acids and are classified based on the length and saturation characteristics of the carbon chain. Fatty acids having 2 to 14 carbons are typically saturated. Longer chain fatty acids having from 16 to 24 or more carbons may be saturated or unsaturated. In longer chain fatty acids there may be one or more points of unsaturation, giving rise to the terms “monounsaturated” and “polyunsaturated,” respectively. Long chain PUFAs are of particular interest in the present invention.
LC PUFAs are categorized according to the number and position of double bonds in the fatty acids according to a well understood nomenclature. There are two series or families of LC PUFAs, depending on the position of the double bond closest to the methyl end of the fatty acid: the n-3 series contains a double bond at the third carbon, while the n-6 series has no double bond until the sixth carbon. Thus, docosahexaenoic acid (“DHA”) has a chain length of 22 carbons with 6 double bonds beginning with the third carbon from the methyl end and is designated “22:6 n-3”. Other important omega-3 LC PUFAs include eicosapentaenoic acid (“EPA”) which is designated (20:5 n-3) and omega-3 docosapentaenoic acid (“DPA” or “DPAn-3”) which is designated (22:5 n-3). Important omega-6 LC PUFAs include arachidonic acid (“ARA”) which is designated (20:4 n-6), and omega-6 docosapentaenoic acid (“DPA” or “DPAn-6”) which is designated (22:5 n-6).
De novo or “new” synthesis of the omega-3 and omega-6 long chain essential fatty acids such as DHA and ARA does not occur in the human body; however, the body can convert shorter chain fatty acids to LC PUFAs such as DHA and ARA although at very low efficiency. Both omega-3 and omega-6 fatty acids must be part of the nutritional intake since the human body cannot insert double bonds closer to the omega end than the seventh carbon atom counting from that end of the molecule. Thus, all metabolic conversions occur without altering the omega end of the molecule that contains the omega-3 and omega-6 double bonds. Consequently, omega-3 and omega-6 acids are two separate families of essential fatty acids since they are not interconvertible in the human body.
Over the past twenty years, health experts have recommended diets lower in saturated fats and higher in polyunsaturated fats. While this advice has been followed by a number of consumers, the incidence of heart disease, cancer, diabetes and many other debilitating diseases has continued to increase steadily. Scientists agree that the type and source of polyunsaturated fats is as critical as the total quantity of fats. The most common polyunsaturated fats are derived from vegetable matter and are lacking in many long chain fatty acids (most particularly omega-3 LC PUFAs). In addition, the hydrogenation of polyunsaturated fats to create synthetic fats has contributed to the rise of certain health disorders and exacerbated the deficiency in some essential fatty acids. Indeed, many medical conditions have been identified as benefiting from omega-3 supplementation. These include acne, allergies, Alzheimer's, arthritis, atherosclerosis, breast cysts, cancer, cystic fibrosis, diabetes, eczema, hypertension, hyperactivity, intestinal disorders, kidney dysfunction, leukemia, and multiple sclerosis. Of note, the World Health Organization has recommended that infant formulas be enriched with omega-3 fatty acids.
The polyunsaturates derived from meat contain significant amounts of omega-6 but little or no omega-3. While omega-6 and omega-3 fatty acids are both necessary for good health, they are preferably consumed in a balance of about 4:1. Concerned consumers have begun to look for health food supplements to restore the equilibrium. Principal sources of omega-3s are flaxseed oil and fish oils. The past decade has seen rapid growth in the production of flaxseed and fish oils. Both types of oil are considered good dietary sources of omega-3 polyunsaturated fats. Flaxseed oil contains no EPA, DHA, or DPA but rather contains linolenic acid—a building block that can be elongated by the body to build longer chain PUFAs. There is evidence, however, that the rate of metabolic conversion can be slow and unsteady, particularly among those with impaired health. Fish oils vary considerably in the type and level of fatty acid composition depending on the particular species and their diets. For example, fish raised by aquaculture tend to have a lower level of omega-3 fatty acids than fish from the wild. In light of the health benefits of such omega-3 and omega-6 LC PUFAs, it would be desirable to supplement foods with such fatty acids.
Due to the scarcity of sources of omega-3 LC PUFAs, typical home-prepared and convenience foods are low in both omega-3 PUFAs and omega-3 LC PUFAs, such as docosahexaneoic acid, docosapentaenoic acid, and eicosapentaenoic acid. In light of the health benefits of such omega-3 PUFAs, it would be desirable to supplement foods with such fatty acids.
While foods and dietary supplements prepared with such PUFAs may be healthier, they also have an increased vulnerability to rancidity. Rancidity in lipids, such as unsaturated fatty acids, is associated with oxidation off-flavor development. The off-flavor development involves food deterioration affecting flavor, aroma, color, texture, and the nutritional value of the particular food. A primary source of off-flavor development in lipids, and consequently the products that contain them, is the chemical reaction of lipids with oxygen. The rate at which this oxidation reaction proceeds has generally been understood to be affected by factors such as temperature, degree of unsaturation of the lipids, oxygen level, ultraviolet light exposure, presence of trace amounts of pro-oxidant metals (such as iron, copper, or nickel), lipoxidase enzymes, free radicals and so forth.
The susceptibility and rate of oxidation of the unsaturated fatty acids can rise dramatically as a function of increasing degree of unsaturation. In this regard, EPA and DHA contain five and six double bonds, respectively. This high level of unsaturation renders the omega-3 fatty acids readily oxidizable. The natural instability of such oils may give rise to unpleasant odor and unsavory flavor characteristics even after a relatively short period of time.
As stated previously it is also desirable to increase intake of other beneficial nutrients. Various sources, including certain types of microalgae and fungi, as well as plant sources, e.g., seeds and animal sources, e.g., aquatic animals, are nutrient dense sources of glycoproteins, vitamins, minerals, simple and complex carbohydrates, antioxidants, amino acids, lipids and other bioactive compounds. However, the unpleasant taste and/or texture of some of these sources has precluded their widespread incorporation into food products. Furthermore, because of the complex biochemical nature of their cell walls, the digestibility of certain microorganisms and seeds and the resulting bioavailability of their nutrients would likely be limited if they were ingested whole and intact.
Instead, selected nutrients are typically extracted from these sources for use in nutritional and/or pharmaceutical products. For example, DHA-rich microbial oil is manufactured from the dinoflagellate Crypthecodinium cohnii and ARA-rich oil is manufactured from the filamentous fungus Mortierella alpina, both for use as nutritional supplements and in food products such as infant formula. Similarly, DHA-rich microbial oil from Schizochytrium is manufactured for use as a nutritional supplement or food ingredient. Typically, the LC PUFAs are extracted from biomass and purified. The extracted and purified oils can be further processed to achieve specific formulations for use in food products (such as a dry powder or liquid emulsion).
It would be desirable to produce a composition comprising nutrient-rich biomass in a form that is easily digested, that exhibits a high nutrient bioavailability, is stable in terms of oxidation, and has acceptable organoleptic characteristics. Especially desirable would be such a composition comprising a PUFA-rich microorganism that exhibits a high oxidative stability. It would be additionally desirable to produce such a composition that is available in either a liquid form or a dry form to accommodate a variety of food and pharmaceutical applications. It would be further desirable to provide a low cost method for making such a composition, said method involving the use of non-hazardous materials, minimal processing steps, and minimal raw material inventory.